scholarly journals Investigation on the Properties and on the Photo-Oxidation Behaviour of Polypropylene/Fumed Silica Nanocomposites

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2673
Author(s):  
Vincenzo Titone ◽  
Maria Chiara Mistretta ◽  
Luigi Botta ◽  
Francesco Paolo La Mantia
Keyword(s):  
Silica Nanoparticles ◽  
Fumed Silica ◽  
Thermomechanical Properties ◽  
Silica Content ◽  
Oxidation Behaviour ◽  
Photo Oxidation ◽  
Polypropylene Nanocomposites ◽  
The Matrix ◽  
Twin Screw ◽  
The Difference

This work investigates the effects of very small amounts of fumed silica on the morphology and on the rheological and mechanical behaviour of polypropylene nanocomposites and on their photo-oxidation behaviour. Polypropylene nanocomposites were prepared using a twin-screw corotating extruder with 0, 1 and 2 wt/wt% of SiO2. Morphological, mechanical, thermomechanical and rheological properties were examined. It was found that the viscosity of the matrix is reduced by the presence of the silica nanoparticles, suggesting a poor adhesion between the two phases and probably some lubricating effect. On the contrary, the mechanical and, in particular, the thermomechanical properties of the matrix are considerably improved by the presence of the silica. In particular, elastic modulus and tensile strength increases remarkably, and this effect becomes more and more remarkable with an increasing temperature. As for the photo-oxidation behaviour, the presence of silica improves the photostability of the polypropylene matrix. This effect has been attributed to both the barrier to the oxygen and to the absorbance of the UV radiation from the silica nanoparticles. Finally, no significant effect of the silica nanoparticles has been put in evidence on the crystallisation behaviour of the polypropylene. As for the effect of the silica content, the difference in the properties of the two nanocomposites is relatively small and all the measured properties depend much less than linearly with its amount. This has been correlated with the reaggregation of the nanoparticles that, having a larger size, decrease the contact area between the matrix and the filler.

Effect of different silane coupling agents on cryogenic properties of silica-reinforced epoxy composites

2016 ◽  
Vol 30 (1) ◽  
pp. 24-37 ◽  
Author(s):  
Hongyu Wang ◽  
Tao Sun ◽  
Cong Peng ◽  
Zhanjun Wu
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Tensile Properties ◽  
Silica Content ◽  
Coupling Agents ◽  
Silane Coupling Agents ◽  
Silane Coupling ◽  
The Matrix ◽  
Dispersion State ◽  
The Difference

Epoxy-based composites containing silica modified by various silane coupling agents (SCAs) were prepared. The effect of the SCAs and the silica content on the thermal, mechanical properties, and fracture toughness of the nanocomposites was investigated. The particle size and dispersion state of the modified silica particles in the matrix were determined by transmission electron microscopy. The modification of silica with SCAs was verified by Fourier transform infrared spectroscopy. The specific tensile properties at ambient temperature (AT, 298 K) were compared with those at cryogenic (LT, 77 K) condition for silica content of 1−5 wt%. The effect of certain types of coupling agents on the thermal properties of the composites was also investigated. The Tg of all amino-silane-modified composites tended to be improved at low silica contents, while that of epoxy-silane-modified composites seemed to be enhanced further at high silica content. The tensile properties of the nanocomposites both at AT and LT tended to be enhanced at lower silica content, especially the failure strain. The fracture toughness ( KIC) turned out to be better enhanced by coupling agents at LT. The difference of the toughening mechanism at AT and LT was examined according to the morphology of the fracture surfaces using the scanning electron microscopy.

Mechanical Properties of Fumed Silica/PP Composites

2014 ◽  
Vol 665 ◽  
pp. 319-322
Author(s):  
Hai Qing Ma ◽  
Zheng Jin ◽  
Wen Long Li ◽  
Di Wu ◽  
Jing Zhao
Keyword(s):  
Mechanical Properties ◽  
Fumed Silica ◽  
Polarized Light ◽  
Silica Content ◽  
Mixing Process ◽  
Melt Mixing ◽  
Dispersion Degree ◽  
Twin Screw ◽  
Pp Composites ◽  
Properties Of Composites

Polypropylene/fumed silica composites were prepared via melt mixing using a twin-screw co-rotating extruder. To improve the dispersion degree of the fumed silica, γ-aminopropyl triethoxy silane (KH-550) was used as silane coupling agent. The PP composites which obtained different fumed silica content were prepared by melt-mixing process. Then composites mechanical properties were measured by the crystal polarized light microscopy (PLM), hardness, tensile testing and so on. The results indicate that fumed silica could toughen PP resin and mechanical properties of composites were optimum when fumed silica content was 1.5 wt%.

scholarly journals Enhanced Olefin Transport by SiO2 Particles for Polymer/Ag Metal/Electron Acceptor Composite Membranes

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2316
Author(s):  
Sang Wook Kang
Keyword(s):  
Silica Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Fumed Silica ◽  
Weight Ratio ◽  
Composite Membranes ◽  
Silica Content ◽  
Mixed Gas ◽  
Scanning Calorimetry ◽  
Fumed Silica Nanoparticles ◽  
Silver Metal

We showed the potential of poly(ethylene-co-propylene) (EPR)/silver metal/p-benzoquinone composite membranes for propylene/propane mixtures, i.e., a selectivity of 10 and a mixed gas permeance of 0.5 GPU (1 GPU = 1 × 10−6 cm3 (STP)/(cm2 s cmHg) in a previous study. In this study, we additionally found that the incorporation of fumed silica nanoparticles into EPR/silver metal/p-benzoquinone (p-BQ) composite membranes exhibited much higher permeance and selectivity for propylene/propane mixtures. The positive polarity of silver metal continuously increased with the increasing silica content up to the 0.1 weight ratio, as revealed by x-ray photoelectron spectroscopy (XPS). This increase in the polarity of silver metal was attributed to the enhanced interaction of p-BQ with the surface of Ag nanoparticles by the increased dispersion of p-BQ by fumed silica nanoparticles. Differential scanning calorimetry (DSC) also presented that the glass transition temperature (Tg) of the membranes was almost invariant. Therefore, the improvement of the permeance and selectivity with the silica nanoparticles was attributable to the increased polarity of the silver metal rather than the structural change.

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

Tem analysis of multiple-energy arsenic implanted and Rta'd silicon

1987 ◽  
Vol 45 ◽  
pp. 246-247
Author(s):  
R.A. Herring
Keyword(s):  
Device Fabrication ◽  
High Concentration ◽  
Tem Analysis ◽  
Defect Clusters ◽  
High Fluences ◽  
Small Defect ◽  
Before And After ◽  
The Matrix ◽  
The Difference ◽  
Factor Type

Rapid thermal annealing (RTA) of ion-implanted Si is important for device fabrication. The defect structures of 2.5, 4.0, and 6.0 MeV As-implanted silicon irradiated to fluences of 2E14, 4E14, and 6E14, respectively, have been analyzed by electron diffraction both before and after RTA at 1100°C for 10 seconds. At such high fluences and energies the implanted As ions change the Si from crystalline to amorphous. Three distinct amorphous regions emerge due to the three implantation energies used (Fig. 1). The amorphous regions are separated from each other by crystalline Si (marked L1, L2, and L3 in Fig. 1) which contains a high concentration of small defect clusters. The small defect clusters were similar to what had been determined earlier as being amorphous zones since their contrast was principally of the structure-factor type that arises due to the difference in extinction distance between the matrix and damage regions.

Development of Prolonged Delivery of Tramadol and Dissolution Translation by Statistical Data Treatment

2011 ◽  
Vol 4 (1) ◽  
pp. 1331-1337
Author(s):  
P B Parejiya ◽  
B S Barot ◽  
P K Shelat
Keyword(s):  
Drug Release ◽  
Study Data ◽  
Stability Study ◽  
Dissolution Time ◽  
Matrix Tablet ◽  
Burst Effect ◽  
The Matrix ◽  
The Mean ◽  
The Difference ◽  
Dissolution Efficiency

The present study was carried out to fabricate a prolonged design for tramadol using Kollidon SR (Polyvinyl acetate and povidone based matrix retarding polymer). Matrix tablet formulations were prepared by direct compression of Kollidon SR of a varying proportion with a fixed percentage of tramadol. Tablets containing a 1:0.5 (Drug: Kollidon SR) ratio exhibited a rapid rate of drug release with an initial burst effect. Incorporation of more Kollidon SR in the matrix tablet extended the release of drug with subsequent minimization of the burst effect as confirmed by the mean dissolution time, dissolution efficiency and f2 value. Among the formulation batches, a direct relationship was obtained between release rate and the percentage of Kollidon SR used. The formulation showed close resemblance to the commercial product Contramal and compliance with USP specification. The results were explored and explained by the difference of micromeritic characteristics of the polymers and blend of drug with excipients. Insignificant effects of various factors, e.g. pH of dissolution media, ionic strength, speed of paddle were found on the drug release from Kollidon-SR matrix. The formulation followed the Higuchi kinetic model of drug release. Stability study data indicated stable character of Batch T6 after short-term stability study.

Impact of AMSU-A Radiances in a Column Ensemble Kalman Filter

2018 ◽  
Vol 146 (12) ◽  
pp. 3949-3976 ◽  
Author(s):  
Herschel L. Mitchell ◽  
P. L. Houtekamer ◽  
Sylvain Heilliette
Keyword(s):  
Covariance Matrix ◽  
Background Error ◽  
Error Covariance Matrix ◽  
Background Error Covariance ◽  
Error Covariance ◽  
Microwave Sounding Unit ◽  
The Matrix ◽  
Microwave Sounding ◽  
Background Temperature ◽  
The Difference

Abstract A column EnKF, based on the Canadian global EnKF and using the RTTOV radiative transfer (RT) model, is employed to investigate issues relating to the EnKF assimilation of Advanced Microwave Sounding Unit-A (AMSU-A) radiance measurements. Experiments are performed with large and small ensembles, with and without localization. Three different descriptions of background temperature error are considered: 1) using analytical vertical modes and hypothetical spectra, 2) using the vertical modes and spectrum of a covariance matrix obtained from the global EnKF after 2 weeks of cycling, and 3) using the vertical modes and spectrum of the static background error covariance matrix employed to initiate a global data assimilation cycle. It is found that the EnKF performs well in some of the experiments with background error description 1, and yields modest error reductions with background error description 3. However, the EnKF is virtually unable to reduce the background error (even when using a large ensemble) with background error description 2. To analyze these results, the different background error descriptions are viewed through the prism of the RT model by comparing the trace of the matrix , where is the RT model and is the background error covariance matrix. Indeed, this comparison is found to explain the difference in the results obtained, which relates to the degree to which deep modes are, or are not, present in the different background error covariances. The results suggest that, after 2 weeks of cycling, the global EnKF has virtually eliminated all background error structures that can be “seen” by the AMSU-A radiances.

V.—Mr. Harkee and Mr. Debley on the Scandinavian Ice-Sheet

1894 ◽  
Vol 1 (11) ◽  
pp. 496-499
Author(s):  
Henry H. Howorth
Keyword(s):  
Ice Sheet ◽  
Good Effect ◽  
The North ◽  
The Matrix ◽  
Glacier Ice ◽  
Inductive Methods ◽  
The North Sea ◽  
Antarctic Continent ◽  
The Alps ◽  
The Difference

Mr. Deeley tells your readers that he has recently been to the summit of Mont Blanc, and has been studying the difference between névé and glacier ice. This is interesting; but we thought that a great many people had done the same thing during the last hundred years, and we thought that one of them, Forbes, had studied the famous Mountain and the phenomenoninquestion to good effect, not in a casual visit to the Alps, but in the course of many years of patient labour. Among other things we also thought he had shown that in a viscous body like ice, the slope of the upper surface necessary to make it begin to move is the same as the slope which, would be required to induce motion in the ice if its bed were inclined at an angle. He further collected considerable evidence to show what the least angle is upon which ice will begin to move. This is the slope, the least slope, available. It is nothing less than astounding to me that anyone should venture to postulate a Scand in avian ice-sheet in the North Sea until he had considered this necessary factor, and how it would operate.The Scand in avian ice-sheet was, I believe, the invention of Croll, who, sittinginhis arm-chair and endowed with a brilliant imagination, imposed upon sober science this extraordinary postulate. He did not dream of testing it by an examination of the coasts of Norway, or even of Britain, but put it forward apparently as a magnificent deduction. All deductions untested by experiment are dangerous. Thus it came about that the great monster which is said to have come from Norway, goodness knows by what mechanical process, speedily dissolved away on the application of inductive methods. Of course it still maintained its hold upon that section, of geologists who dogmatiseinprint a great deal about the Glacial period before they have ever seen a glacier at work at all; but I am speaking of those who have studied the problem inductively. First Mr. James Geikie, a disciple of Croll, was obliged to confess that this ice-sheet, which is actually said to have advanced as far as the hundred-fathom line in the Atlantic, and there presented a cliff of ice like the Antarctic continent, never can have reached the Faroes, which had an ice-sheet of their own. Next Messrs. Peach and Home were constrained to admit that no traces of it of any kind occur in the Orkneys, or in Eastern Scotland. They still maintained its presence in the Shetlands; however, this was upon evidence which is somewhat extraordinary. I do not mean the evidence as to the direction of the striation, which was so roughly handled by Mr. Milne-Home, but I mean the evidence they adduce that the boulders found on the islands are apparently all local ones, and that, contrary to the deposits of glaciers, they diminish in number as we recede from the matrix whence they were derived.

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